A processing step of separating an aggregate material into various components has proved highly valuable in modern industrial processes. Many different separation techniques have been utilized in the past with these techniques relying on differing characteristics of the components of the aggregate, such as size, weight, specific gravity, solubility in different solvents, etc. It has long been recognized in certain industrial processes that the separation of a particulate material into magnetic and non-magnetic components has particular utility. Among various magnetic separation apparatus, two particular assemblies enjoy wide-spread use in the dry and wet separation of particulate materials.
A first type of magnetic separation apparatus is known as a high-intensity magnetic roll separator. Typically, a magnetic roll separator is configured to have a cylindrical magnetic roller located at a downstream end and a cylindrical idler roller located an upstream end. A relatively thin conveyor belt encircles the magnetic roller and the idler roller to convey the particulate material for discharge at the magnetic roller end. Material to be separated is therefore deposited on an upper conveying portion of the belt at an upstream end so that it is advanced towards the downstream end and is discharged as the conveyor belt moves around the magnetic roller. Magnetic components are attracted to the magnetic roller and thus have a different discharged trajectory than non-magnetic components as the various particles leave the conveyor belt at the discharge region associated with the magnetic roller. An example of such a magnetic roller assembly is shown in my U.S. Pat. No. 5,101,980 issued Apr. 7, 1992.
A second type of magnetic separation apparatus for use in separating both dry and wet, particulate aggregated or slurried material is that known as a drum separator. A typical drum separator is constructed to have a drum formed as a cylindrical shell which is rotatably journaled onto a horizontal axis. Particulate material is introduced on the outer cylindrical surface of the drum and, as the drum rotates, this particulate material is advanced and is discharged under the force of gravity so as to have a discharge trajectory. A magnetic array is disposed internally of the drum and is located proximate to the drum sidewall. The magnetic array is positioned to interact with the particulate material before it is discharged from the drum surface. Thus, as the particulate material moves past the magnetic array, the magnetic attraction between certain components of the particulate material tend to adhere to the drum surface longer than non-magnetic components. Moreover, different magnetic components of the aggregate have varying strengths of interaction with the magnetic field from the magnet array so that the differing magnetic components as well as non-magnetic components have different discharge trajectories from the drum due to a combination of the magnetic force and the gravitational and inertial forces. The differing streams of particulate materials may be separated by simple partition walls either in chutes, bins or the like, and the separated components may be further processed and refined for purity.
The present invention is directed to this second type of magnetic separation apparatus, and the present invention is constructed to provide advantages over existing magnetic drum separators. For example, one difficulty in the construction of magnetic drum separators is the organization of a magnetic array which provides a magnetic field of sufficient strength to adequately interact with the magnetic components of the feed material. Whereas magnetic roll separators are able to use conveyor belts which are relatively thin and flexible, the drum of a magnetic drum separator must be of sufficient mechanical strength and rigidity to minimize deflection of the drum sidewall for large drum separators and otherwise to support the weight of the particulate material (usually crushed ore). This requires the drums to be constructed of a non-magnetic metal or a non-conductive material having a sufficient sidewall thickness to provide the requisite structural integrity. By having a thicker sidewall, the particulate material is by necessity located an increased distance from the magnetic array than that achieved, for example, by the magnetic roll separator. This of course diminishes the strength of the magnetic field at the outer surface of the drum.
Further, due to the typical construction of the rotating drum sidewall out of a non-magnetic metal material, the movement of the sidewall through the magnetic field causes the induction of eddy currents having their own electric magnetic field components. Since the force of these fields interacting with the magnetic field from the magnetic array must be overcome by the mechanical drive for the drum itself, the support structure for the magnetic array and the drum must be adequately designed, especially where the magnetic array provides superior magnetic field strength.